Comparison circuits are widely used in conversion process between the analog signals and the digital signals (A/D conversion) which the sampled analog signal will be flowed through an operational amplifier or a comparator to determine its digital value. This operational amplifier utilizes an open-loop mode commonly that no compensation for the operational amplifier is needed, so that the operational amplifier may obtain a wider bandwidth and a higher frequency response. However, it's known that mutual restraint appears in the gain and the comparison speed of the amplifier always, which causes a difficulty to achieve both quick comparison and high accuracy at a certain process condition.
Therefore, there is a need for an improved quick comparison circuit to overcome the above-mentioned drawbacks.